Method and device for the friction stir welding of two components

ABSTRACT

A method for the friction stir welding of two components, in particular of two shell components of a fuselage structure of an aircraft and spacecraft, said method comprising the following method steps: positioning the two components relative to one another in such a way that a connection region is formed between the two components; friction stir welding the two components by a friction stir welding tool which penetrates the connection region in order to produce a weld which permeates the connection region with the formation of an unpenetrated weld edge portion of the connection region; and introducing internal compressive stresses, at least in the weld edge portion of the connection region. Further a device for the friction stir welding of two components, in particular of two shell components of a fuselage structure of an aircraft and spacecraft is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of and claims priority to U.S.application Ser. No. 13/077,117 filed Mar. 31, 2011, which claims thebenefit of and priority to U.S. Provisional Application No. 61/321,990,filed Apr. 8, 2010 and German Patent Application No. 10 2010 003 742.7,filed Apr. 8, 2010, the entire disclosures of which are incorporated byreference herein.

TECHNICAL FIELD

The present invention relates to a method and a device for the frictionstir welding of two components, in particular of two shell components ofa fuselage structure of an aircraft and spacecraft.

BACKGROUND

In passenger aircraft and transport aircraft construction aluminiumfuselage shell segments are generally riveted together alonglongitudinal seams. This requires, in addition to an overlap between thecomponents to be connected in the seam region, a large number ofindividual components that have to be used. Rivet connections of thistype are thus expensive to produce and signify an undesired increase inweight in the seam region.

An alternative joining method for connecting thin-walled aluminiumcomponents of this type is known as friction stir welding. In thisinstance a rotating tool with a tool pin protruding from a tool shoulderis pressed into a connection region between two components to beconnected until the tool shoulder rests on the component surfacesadjacent to the connection region. The components lie on a support. Theshoulder heats the component surfaces adjacent to the connection regionby friction, thus heating the material of the components to just belowthe melting point. The tool is then moved along the connection regionwhilst maintaining the contact pressing force, the tool pin mixingplasticised material in the connection region. In order to prevent thecomponents from being welded to the support, the penetration depth ofthe welding tool is set in such a way that the connection region is notfully penetrated. The size of this remaining unpenetrated region of theconnection region is to be maintained in the order of a few tenths of amillimetre. If the depth of the remaining region exceeds a tolerancelimit, ‘penetration defects’ or ‘LOP’ (lack of penetration) defects maybe produced owing to internal tensile stresses induced in the materialand insufficient material plasticisation. Such LOP defects significantlyreduce the fatigue limit of welds produced by friction stir welding.

However, when welding large components with long welds, for example asis the case when constructing fuselage and aerofoil sections, compliancewith such narrow tolerances is hugely complex from a technical point ofview and is therefore virtually impossible. It is possible for exampleto use a ‘bobbin friction stir welding tool’ in order nevertheless toeliminate the formation of LOP defects. In contrast to the conventionalfriction stir welding pin tool, this bobbin friction stir welding toolis applied to the connection region from two sides, thus ensuring thatthe connection region is always fully penetrated. In this instancehowever, the connection region must be accessible from each side.Furthermore, when using this tool the weld is visible from each side,which is not desirable for example when connecting two components whichform a visible surface. Furthermore, the use of the bobbin friction stirwelding tool means that the time and therefore cost involved is highercompared to the friction stir welding pin tool.

An alternative to the use of a bobbin friction stir welding tool is theuse of a conventional friction stir welding pin tool in combination witha further method step in which the region with possible LOP defects isremoved by machining, for example by milling. This means that the weldmust not extend through a visible surface since ghost lines would thenbe visible. This finishing, by machining, of the connection region alsoinvolves considerable additional time.

SUMMARY

The object of the present invention is therefore to provide an improvedmethod for connecting two components, which method does not have theaforementioned drawbacks.

A method for the friction stir welding of two components, in particularof two shell components of a fuselage structure of an aircraft andspacecraft, is accordingly provided and comprises the following methodsteps: positioning the two components relative to one another in such away that a connection region is formed between the two components;friction stir welding the two components by means of a friction stirwelding tool which penetrates the connection region in order to producea weld which permeates the connection region with the formation of anunpenetrated weld edge portion of the connection region; and introducinginternal compressive stresses, at least in the weld edge portion of theconnection region.

A device for the friction stir welding of two components, in particularof two shell components of a fuselage structure of an aircraft andspacecraft, is further provided and comprises a positioning means forpositioning the two components relative to one another in such a waythat a connection region is formed between the two components; afriction stir welding tool which can be applied in the connection regionand which penetrates the connection region to produce a weld whichpermeates the connection region with the formation of an unpenetratedweld edge portion of the connection region; and a compressive stressgeneration means for introducing internal compressive stresses, at leastinto the weld edge portion of the connection region.

The idea on which the present invention is based is that internalcompressive stresses are introduced at least into the weld edge portionof the connection region of the friction stir weld. These internalcompressive stresses which are introduced prevent the formation andspread of microcracks in the connection region since they offsetinternal tensile stresses in the weld edge portion which are introducedduring the friction stir welding process and non-positively seal anydefects which have already formed. Both the fatigue limit and theresidual strength can thus advantageously be increased in the region ofthe friction stir weld to the value of the base material of the weldedcomponents.

The present invention thus provides a method and a device which, incontrast to existing joining methods, make it possible to connectlarge-surface components in a rapid and reliable manner with minimalmaterial usage.

Advantageous configurations and developments of the present inventionwill emerge from the dependent claims and from the description inconjunction with the figures shown in the drawings.

In accordance with a preferred development of the method according tothe invention, the weld penetrates the components starting from a firstsurface of the components, and the internal compressive stresses areintroduced from a second surface, which is opposite the first surface,of the components, at least in the weld edge portion of the connectionregion. It is thus advantageously possible for the internal compressivestresses to be introduced exclusively into those regions of thecomponents where there is an increased risk of the formation ofpenetration defects.

In accordance with a further preferred development of the methodaccording to the invention the internal compressive stresses areintroduced up to a depth of the connection region which is greater thana depth of the weld edge portion of the connection region, the depth ofthe weld edge portion being 0.2 to 0.4 mm in particular. Internaltensile stresses, which promote crack formation and crack development,are thus reliably prevented in the material of the weld edge portion.

In accordance with a further preferred development of the methodaccording to the invention the dynamic yield strength, at least of thematerial of the weld edge portion, is exceeded locally in order toproduce the internal compressive stresses, whereby the material isplastically deformed locally, thus closing microcracks which areproduced in the weld edge portion by means of the friction stir weldingprocess. This reliably prevents any spreading of microcracks which havealready been formed.

In accordance with a further preferred development of the methodaccording to the invention the internal compressive stresses areintroduced in an internal compressive stress region of influence in atransverse direction of the weld, which internal compressive stressregion of influence is broader than a thermo-mechanical zone ofinfluence formed by means of the friction stir welding tool along theweld. Internal compressive stresses are thus applied to the entireregion of the components which is affected by the welding process.

In accordance with a further preferred development of the methodaccording to the invention the internal compressive stresses aregenerated by means of laser shock peening, pulsed laser beams preferablybeing used. It is thus possible to introduce internal compressivestresses into the components in a contactless manner, thus simplifyingthe method according to the invention and accelerating the applicationthereof.

In accordance with a further preferred development of the methodaccording to the invention, before the laser shock peening an opaquelayer is applied to the components, at least over portions, to improveshock wave propagation in the components and to act as a sacrificiallayer, and before the laser shock peening a transparent layer, inparticular a layer formed of flowing water, is applied to the opaquelayer to prevent reflection of the laser beam and to form a spatiallydefined plasma in the transparent layer. It is thus reliably ensuredthat shock waves which are large enough to form the internal compressivestresses are introduced into the components. The surface of thecomponents is further prevented from being damaged since the opaquelayer acts as a removable sacrificial layer.

In accordance with a further preferred development of the methodaccording to the invention the internal compressive stresses areproduced by means of low plasticity burnishing. This makes it possible,in addition to the introduction of internal compressive stresses, toimprove surface quality by smoothing the component surface in the regionof the weld.

In accordance with a further preferred development of the methodaccording to the invention the internal compressive stresses aregenerated by means of ultrasonic peening. This makes it possible to alsouse the method at points which are not easily accessible, thus extendingthe scope of use of the method.

In accordance with a further preferred development of the methodaccording to the invention the weld formed is configured as a butt weld.This makes it possible to connect the components without an overlap,thus advantageously making a saving in terms of weight.

In accordance with a further preferred development of the methodaccording to the invention the internal compressive stresses areintroduced at the same time as or in a chronologically staggered mannerwith regard to the formation of the weld. The introduction of thecompressive stresses at the same time as the formation of the weld makesit possible to carry out the method according to the invention in aparticularly rapid and cost-effective manner. By contrast, theintroduction of the internal compressive stresses in a chronologicallystaggered manner with regard to the formation of the weld makes itpossible to spatially separate the steps of introducing the internalcompressive stresses and welding the components, the device for carryingout the method for friction stir welding of two components thus beingcomposed in a particularly simple and cost-effective manner.

In accordance with a further preferred development of the methodaccording to the invention the components are placed on a support restfor positioning and/or friction stir welding. This makes it possible toposition the components reliably and precisely relative to one another,thus increasing the quality of the weld formed.

In accordance with a preferred development of the device according tothe invention the compressive stress generation means is formed as alaser means for generating pulsed laser beams. This advantageously makesit possible to introduce the internal compressive stresses into theconnection region of the components in a contactless and rapid manner.

In accordance with a further preferred development of the deviceaccording to the invention the positioning means is formed as a supportrest. This makes it possible to position the components relative to oneanother in a simple and convenient manner.

The configurations and developments above can be combined in anyappropriate manner.

In the following, the invention is described in further detail on thebasis of embodiments with reference to the accompanying figures of thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures:

FIG. 1 is a front view of a preferred embodiment of a device for thefriction stir welding of two components;

FIG. 2 is a cross-sectional view of the preferred embodiment of thedevice according to FIG. 1;

FIG. 3 is a plan view of two components to be welded;

FIG. 4 is a cross-sectional view of a weld;

FIG. 5 is a side view of a further embodiment of a device for thefriction stir welding of two components;

FIG. 6 is a cross-sectional view through two welded components; and

FIG. 7 is a perspective view of a fuselage section with a longitudinalseam.

DETAILED DESCRIPTION

In the figures, like reference numerals refer to like or functionallysimilar components unless information to the contrary is given.

A preferred embodiment of the present invention will be describedhereinafter with reference to FIGS. 1 to 7.

FIG. 1 shows a device 26 for the friction stir welding of two components1, 2. The device 26 comprises a positioning means 27, which ispreferably formed as a support rest 27 in the form of a plate-shapedrest, and a friction stir welding tool 7. The positioning means 27 is anoptional component of the device 26. The friction stir welding tool 7can be moved towards the positioning means 27 in the vertical direction.This possibility for movement is illustrated by the arrow 30. Asillustrated by the arrow 31, the friction stir welding tool 7 is movablealong a connection region 6 formed between the two components 1, 2. Thefriction stir welding tool 7 is substantially cylindrical. For example,it comprises a cylinder 39 with a first end face formed as a toolshoulder 36. For example a truncated cone 38 or a ‘tool pin’ 38 isarranged on the tool shoulder and has a smaller base diameter than thecylinder 39. The cylinder 39 and the truncated cone 38 are arranged soas to be collinear. An axial length l of the tool pin 38 correspondsapproximately to a thickness d of the components 1, 2 to be welded. Thefriction stir welding tool is rotatable about an axis of rotation 32.This rotary movement is illustrated by means of the arrow 33.

The device 26 further comprises a compressive stress generation means 28which is formed for example as a laser means 28 for the generation ofpulsed laser beams.

The method steps for the friction stir welding of the two components 1,2 will be described hereinafter. The two components 1, 2 are firstpreferably positioned relative to one another by means of thepositioning means 27, in such a way that the connection region 6 isformed between the two components 1, 2. For this purpose the twocomponents 1, 2 are placed for example on the support rest 27 and sidefaces 34, 35 of the components 1, 2 are positioned so as to be incontact. The connection region 6 comprises the side faces 34, 35 and endportions 45, 46, associated with the side faces 34, 35, of thecomponents 1, 2. The side faces 34, 35 of the components 1, 2 preferablycontact in the connection region 6. For example the components 1, 2 arefixed on the support rest 27 against slipping, preferably by clampingmeans (not shown). Preferably, the support rest 27 is formed as a vacuumtable or the support rest 27 comprises a vacuum means, the components 1,2 being fixable on the support rest 27 by means of the application of avacuum.

The friction stir welding tool 7 is rotated and moved in the directionof a first surface 10 of the components 1, 2. The rotating friction stirwelding tool 7 is pressed into the connection region 6 with a highcontact pressing force 44 until the tool shoulder 36 comes to rest onthe first surface 10. This is illustrated in FIG. 2. The tool pin 38 andthe friction stir welding tool 7 penetrate the connection region 6,although not fully. The friction between the tool shoulder 36 and thefirst surface 10 of the components 1, 2 heats the material beneath theshoulder 36 to just below the melting point of the components 1, 2. Thematerial is thus plasticised and it is possible to mix the materials ofthe components 1, 2 in the connection region 6. The tool pin 38 swirlsthe material. In order to better mix the material the tool pin 38 ispreferably provided with a thread 43 which mixes the plasticisedmaterial of the components 1, 2.

The rotating friction stir welding tool 7 is then moved along theconnection region 6, whilst maintaining the high contact pressing force44. This feed movement in the direction of the arrow 31 produces apressure gradient between a front and a rear face 41, 42 of the tool pin38. The rotary movement of the friction stir welding tool 7 movesplasticised material about the friction stir welding tool 7, where saidmaterial is mixed and forms an approximately V-shaped weld 8 which isillustrated by hatching in FIG. 3. On the one hand the material iscompressed by the force 44 directed vertically towards the surface 10with the introduction of heat, and on the other hand is presseddownwardly towards a weld root 48 as a result of the geometry of therotating tool 7 and the swirling of the partly plastic material. In thisinstance an extrusion duct is formed which extends as far as the weldroot 48 and is also referred to as a weld nugget 47.

This weld 8 ideally fully penetrates the connection region 6 startingfrom the first surface 10. However, the tool pin 38 and the frictionstir welding tool 7 preferably do not fully penetrate the two components1, 2 in the connection region 6, but merely as far as a weld edgeportion 9 of the connection region 6. Full penetration of the components1, 2 by the tool pin 38 is to be avoided, since the components 1, 2 maythus be welded to the support rest 27 and/or the support rest 27 and/orthe tool pin 38 may be damaged. The weld edge portion 9 of theconnection region 6 is preferably also welded by the introduction offrictional heat in the connection region 6 owing to the rotatingfriction stir welding tool 7 and by the mechanical mixing of theplasticised material of the components 1, 2 in the connection region 6,in such a way that the weld 8 fully permeates the connection region 6.Deviating from the aforementioned ideal scenario, the weld 8 penetratesthe weld edge portion 9, which is not penetrated by the tool 7, over alength of the weld 8, but only over portions or else not at all. Forexample the weld edge portion 9 has a thickness t2 of preferably 0.2 toa maximum of 0.4 mm. The thickness t2 is highly dependent on thegeometry of the friction stir welding tool 7 used and on the weldingprocess parameters used, i.e. the thickness t2 can deviate considerablyfrom the aforementioned values depending on the geometry of the toolused and/or on the process parameters used. The thickness t2 is to beprecisely maintained over the entire weld length during the weldingprocess in order to obtain high and constant strengths of the weld 8.This precise maintenance of the thickness t2 can only be achieved withdifficulty, even in a mechanical welding process, for example with useof a robotic arm to position the tool 7. This applies in particular whenwelding large, curved components such as components of aircraftfuselages.

If this thickness t2 is not precisely maintained within theaforementioned tolerance range over the entire length of the weld 8,i.e. if the thickness t2 exceeds the maximum value, which is hugelycostly from a technical point of view in the case of large weld lengthson large components, defects, for example in the form of microcracks 12,may appear in the region of the weld edge portion 9, as is shown in FIG.4. Such defects may occur owing to incomplete plasticisation of thematerials of the components 1, 2 and/or owing to internal tensilestresses induced in the material by the welding process. Internaltensile stresses promote the formation of microcracks 12 and crackgrowth of a microcrack 12 which is already present. Such defects in theweld edge portion 9 caused by insufficient penetration of the frictionstir welding tool 7 are known as LOP (lack of penetration) defects.These LOP defects can considerably reduce the service life of frictionstir welded components 1, 2, in particular friction stir weldedaluminium components.

In order to limit the effect of such LOP defects, produced duringfriction stir welding, on the service life of the weld 8, internalcompressive stresses are introduced in a further method step, at leastinto the weld edge portion 9 of the connection region 6 of the twocomponents 1, 2. These internal compressive stresses are preferablyintroduced from a second surface 11 of the connection region 6, whichsurface is arranged opposite the first surface 10 of the components 1,2. These internal compressive stresses prevent microcracks 12 fromspreading since said microcracks 12 are compressed, so to speak. Theinternal compressive stresses introduced further counteract internaltensile stresses induced in the connection region during the weldingprocess, i.e. they offset said internal tensile stresses. The internalcompressive stresses are preferably introduced up to a depth t1 of theconnection region 6, which depth is preferably greater than the depth t2of the weld edge portion 9 of the connection region 6. Internal tensilestresses are thus reliably prevented from acting in the weld edgeportion 9. Any remaining internal tensile stresses then act merely inthe region of the portion of the connection region 6 penetrated by thetool pin 38.

In order to produce the internal compressive stresses in the material ofthe connection region 6, the dynamic yield strength of the material isexceeded locally, at least in the region of the weld edge portion 9,thus plastically deforming the material locally. The internalcompressive stresses are introduced in an internal compressive stressregion of influence 13 in a transverse direction q of the weld. Theinternal compressive stress region of influence 13 is preferably broaderthan a diameter of the tool pin 38. For example the internal compressivestress region of influence 13 is broader than a diameter of the toolshoulder 36 of the tool 7. This means that the internal compressivestresses are introduced in a planar manner on each side of the weld 8.The thermo-mechanical zone of influence 14 is substantially V-shaped,wherein the open sides of the V point towards the first surface 10.

As illustrated in FIG. 5, the internal compressive stresses arepreferably generated by means of by laser shock peening, wherein pulsedlaser beams 15 are preferably used which are generated by thecompressive stress generation means 28, for example in the form of alaser means 28. The laser shock peening is preferably carried out in achronologically staggered manner with regard to the formation of theweld 8. Alternatively, the internal compressive stresses can also beintroduced into the weld edge portion 9 of the connection region 6 atthe same time as the formation of the weld 8. For this purpose thepositioning means 27 may, for example, comprise a recess which is formedin such a way that the second surface 11 is accessible, at least overportions, for the introduction of the internal compressive stresses. Thepositioning means 27 can alternatively be completely omitted.

With laser shock peening an opaque layer 16, for example in the form ofan aluminium foil, is preferably applied to the components 1, 2, atleast in the region of the connection region 6. This opaque layer 16improves shock wave propagation in the components 1, 2, and it is alsoused as a sacrificial layer, i.e. it is removed again after the lasershock peening process.

A transparent layer 17, in particular a layer of flowing water 17, ispreferably applied to the opaque layer 16. This prevents reflection ofthe laser beam 15 and thus makes it possible to form a spatially definedplasma 19 in the transparent layer 17. The shock waves are generated bythe plasma 19 and therefore only indirectly by the laser beam 15.

The internal compressive stresses can alternatively also be introducedinto the weld edge portion 9 by means of mechanical methods, such as the‘low plasticity burnishing’ (LPB) method. In this instance a steel ballaccommodated in a hydrostatic bearing is guided over the surface of thecomponent, the material of the component being plastically deformedlocally and internal compressive stresses being introduced into thecomponent.

For example ‘ultrasonic peening’ (UP) may also be considered as afurther alternative for the introduction of the internal compressivestresses into the weld edge portion 9. In this instance an ultrasonicsonotrode is placed on the surface of the component. The material of thecomponent is plastically deformed locally, whereby internal compressivestresses are introduced into the component.

FIG. 6 shows a cross-sectional view of the welded components 1, 2, whichare preferably formed as thin-walled metal sheets 22, 23. The metalsheets 22, 23 preferably consist of an aluminium alloy. The method canthus be used, in particular, for the construction of fuselage structuresof aircraft and spacecraft from thin-walled aluminium components. Themetal sheets 22, 23 have thickenings 20, 21 in the region of the weld 8formed as a butt weld 8. As a result of the thickenings 20, 21, morematerial is available for plasticisation in the connection region 6.This makes it possible to form the weld 8 in an improved manner with alarge weld thickness.

FIG. 7 is a schematic view of a fuselage structure 5 of an aircraft andspacecraft. In this case the components 1, 2 are preferably formed asshell components 3, 4, between which the weld 8 is formed as alongitudinal seam 37.

By means of the method according to the invention it is thus possible toconnect large-surface components by long friction stir welds withoutrunning the risk of LOP defects being formed. For example, compared toknown joining methods, shell components of a fuselage structure of anaircraft and spacecraft can thus be reliably connected more quickly,with a greater saving in terms of weight and with lower material usage.

Although the present invention was described with reference to preferredembodiments, it is not limited thereto, but can be modified in manydifferent ways. In particular, features of the individual embodimentsdetailed above can be combined in any appropriate manner.

In a particularly preferred modification of the present invention, themethod according to the invention is used, for example, to connectoverlapping welds, corner welds, T-welds and the like.

The materials, numbers and dimensions stated should be understood to beexemplary and serve merely to explain the embodiments and developmentsof the present invention.

Use of the invention in other fields, in particular in vehicle or marineconstruction, is of course also conceivable.

While at least one exemplary embodiment of the present invention(s) isdisclosed herein, it should be understood that modifications,substitutions and alternatives may be apparent to one of ordinary skillin the art and can be made without departing from the scope of thisdisclosure. This disclosure is intended to cover any adaptations orvariations of the exemplary embodiment(s). In addition, in thisdisclosure, the terms “comprise” or “comprising” do not exclude otherelements or steps, the terms “a” or “one” do not exclude a pluralnumber, and the term “or” means either or both. Furthermore,characteristics or steps which have been described may also be used incombination with other characteristics or steps and in any order unlessthe disclosure or context suggests otherwise. This disclosure herebyincorporates by reference the complete disclosure of any patent orapplication from which it claims benefit or priority.

LIST OF REFERENCE NUMERALS

-   1 component-   2 component-   3 shell component-   4 shell component-   5 fuselage structure-   6 connection region-   7 friction stir welding tool-   8 weld/butt weld-   9 weld edge portion-   10 first surface-   11 second surface-   12 microcracks-   13 internal compressive stress region of influence-   14 thermo-mechanical zone of influence-   15 pulsed laser beam-   16 opaque layer-   17 transparent layer/flowing water-   19 defined plasma-   20 thickening-   21 thickening-   22 metal sheet-   23 metal sheet-   26 device-   27 positioning means/support rest-   28 compressive stress generation means/laser means-   30 arrow-   31 arrow-   32 axis of rotation-   33 arrow-   34 side face-   35 transverse direction-   36 tool shoulder-   37 longitudinal seam-   38 truncated cone/tool pin-   39 cylinder-   41 front face-   42 rear face-   43 thread-   44 contact pressing force-   45 end portion-   46 end portion-   47 weld nugget-   48 weld root-   d component thickness-   l length-   q transverse direction-   t1 thickness-   t2 thickness

1. A method for the friction stir welding of two components, inparticular of two shell components of a fuselage structure of anaircraft and spacecraft, said method comprising the following methodsteps: positioning the two components relative to one another in such away that a connection region is formed between the two components;friction stir welding the two components by a friction stir welding toolwhich penetrates the connection region in order to produce a weld whichpermeates the connection region with the formation of an unpenetratedweld edge portion of the connection region; and introducing internalcompressive stresses, at least in the weld edge portion of theconnection region, wherein the internal compressive stresses aregenerated by ultrasonic peening.
 2. The method according to claim 1,wherein the weld penetrates the components starting from a first surfaceof the components, and wherein the internal compressive stresses areintroduced from a second surface, which is opposite the first surface,of the components, at least in the weld edge portion of the connectionregion.
 3. The method according to claim 1, wherein the internalcompressive stresses are introduced up to a depth of the connectionregion which is greater than a depth of the weld edge portion of theconnection region, the depth of the weld edge portion being 0.2 to 0.4mm in particular.
 4. The method according to claim 1, wherein thedynamic yield strength, at least of the material of the weld edgeportion, is exceeded locally in order to produce the internalcompressive stresses, whereby the material is plastically deformedlocally and microcracks formed in the weld edge portion by the frictionstir welding process are closed.
 5. The method according to claim 1,wherein the internal compressive stresses are introduced in an internalcompressive stress region of influence in a transverse direction of theweld, which internal compressive stress region of influence ispreferably broader than a diameter of a tool pin of the friction stirwelding tool and is more preferably broader than a diameter of a toolshoulder of the friction stir welding tool.
 6. The method according toclaim 1, wherein the weld formed is configured as a butt weld.
 7. Themethod according to claim 1, wherein the internal compressive stressesare introduced at the same time as or in a chronologically staggeredmanner with regard to the formation of the weld.
 8. The method accordingto claim 1, wherein the components are placed on a support rest forpositioning and/or friction stir welding.
 9. A device for the frictionstir welding of two components, in particular of two shell components ofa fuselage structure of an aircraft and spacecraft, comprising: apositioning means for positioning the two components relative to oneanother in such a way that a connection region is formed between the twocomponents; a friction stir welding tool which can be moved into theconnection region and which penetrates the connection region in order toproduce a weld which permeates the connection region with the formationof an unpenetrated weld edge portion of the connection region; and acompressive stress generation means for introducing internal compressivestresses, at least into the weld edge portion of the connection region,wherein the internal compressive stresses are generated by ultrasonicpeening.
 10. The device according to claim 9, wherein the positioningmeans is configured as a support rest.